The present invention pertains generally to double envelope constructions and more particularly to double envelope constructions comprised of two envelopes, one inside the other, formed in one pass on an envelope folding machine.
Double envelopes have become quite popular and are commonly used to send material to addressees in the outer envelope and to enable the addressees to return material to the sender in the inner envelope. In such case, the inner envelope is usually preprinted with the address of the sender. Double envelopes are also used to send material to addressees some of which, such as documents, tickets, stamps, coupons and the like, is contained in the inner envelope.
Double envelope constructions in use today are generally made by separately forming the inner and outer envelopes and then inserting the inner one into the outer one. The separate manufacture of the two envelopes as well as the required step of inserting the inner envelope into the outer one increase considerably the cost of manufacturing the double envelopes.